Liquid heater



Patented Jan. 12, i943 unirte sT T .E Si iti @FFME This invention relates to a liquid heater, parjticularly to a heater in which electrical heating through a tube.

A particular feature oi the invention resides in the provision of a tube having internal and external fins, both of which are homogeneously integral with the tube, the electrical heating elements being disposed in eicient heat-conducting relation with the external hns.

These and other objects and advantages of the invention will become apparent as the description proceeds.

While a preferred form of the invention is disclosed for purposes of illustration, it should be understood that various changes may be made vithout departing from the spirit of the invenion.

In the drawing:

Fig. 1 is a semi-diagrammatic plan view, partly in section, illustrating one embodiment of the invention.

Fig. 2 is an enlarged section on line 2 2 Fig. 1.

Fig. 3 is an enlarged section on line 3 3 of Fig. 1.

Referring to the drawing more particularly, the heater involves the use of a single continuous length of tubing l0 provided with internal nhs Il and external iins l2. disposed opposite some of the external fins to facilitate conduction of heat from the external fins to the internal fins. In some cases it may be desirable to form internal ns opposite each of the external iins, although in the form illustrated an internal iin is located opposite every other external iin. The tube is extruded with I'the ns homogeneously integral therewith of some suitable heat-conducting material, such as aluminum or an alloy thereof.

In order to provide a more enicient heat-conducting contact between the internal ns and the fluid passing through the tube, the tube is twisted so as to give both the internal external ns a spiral form.

Heat is supplied by any suitable electrical heating means, such as the Chromaloy resistant wires I3 which are helically wound and embedded in a suitable heat-conducting dielectric cement such as Alundum cement indicated at It.

Since the coils of heating wire are relatively close to two adjacent external iins I 2 and are Within the arc defining the outer edges of the external fins, they are very effectively disposed The internal fins are to the main body of the tube. The liquid passing through the tube is heated by contact with the walls of the tube, the heating area 0f which is very materially increased by the internal fins H. The spiral form of the internal fins causes turbulence in the stream of liquid, which results in the liquid making elcient heat-absorbing contact with the inner hns l! and inner wall of the tubing.

If it is desired to arrange a considerable length of the heating tube within a relatively small box or container, the tube l0 may be bent back upon itself so as to have several runs of the tube pass through the container as indicated in the form shown in Fig. 1. The portions l5 that are to be bent have the external fins removed, and the internal iins are preferably not twisted at these portions. During the bending operation collapse of the tube and of the internal ns Il is prevented by drawing into this part of the tube a mouse which may be formed of a plurality of flexible elements such as Wires.

Each of the runs of the tubing that is within the box or container i6 will have heating elements disposed in heating relation to the external fins as previously described. The heated runs of the tubing, as well as the bend I5, may be insulated in any well-known manner, the nsulation being indicated at I'l.

The electrical connections for the heating units are indicated diagrammatically. Any preferred means may be used for controlling a supply of electric current to the heating elements, such as a multi-stage manual switch or a thermostatic switch operated by the temperature of the fluid passing from the heating unit.

I claim:

l. A heater which comprises a tube arranged to conduct the liquid to be heated, the tube being seamless and having external spiral iins homogeneously integral therewith, and heating elements Wound spirally and placed between the uns and in heat-conducting relation therewith.

2. A heater which comprises a tube arranged to conduct the liquid to be heated, the tube being seamless and having external spiral iins and internal spiral ns, both sets of fins being homogeneously integral with the tube, and heating elements wound spirally and placed between the U" external hns and in heat-conducting relation therewith.

3. A heater which comprises a tube arranged to conduct the liquid to be heated, the tube being seamless and having external spiral fins and to transfer heat to the external iins i2 as well as 53 internal spiral ns, both sets of nhs being ho mogeneously integral with the tube, the internal ns being arranged directly opposite external ns of the tubing, and heating elements wound spirally and placed between the external fins and in heat-conducting relation therewith.

4. A liquid heater which comprises a tube of extruded aluminum arranged to conduct the liquid to be heated, the tube being seamless and having external and internal spiral fins, both sets of ns being homogeneously integral with the tube, the internal ns being arranged directly opposite external ns of the tubing, and heating elements wound spirally and placed between the external ns and in heat-conducting relation therewith.

5. A liquid heater comprising a continuous length of extruded seamless tubing arranged in a plurality of runs connected by bends, the runs having internal and external spiral fins homogeneously integral with the tube, the internal ns being arranged directly opposite external fins of the tubing, and electrical heating elements placed between the external fins and within the arc bounding the outer edges of the external fins. Y

6. A liquid heater comprising a continuous length of extruded seamless aluminum tubing arranged in a plurality of runs connected by bends, external fins on the runs only, internal iins extending through the entire length of the tubing, all of said fins being homogeneously integral with the tube, the internal ns being arranged directly opposite external ns of the tubing, electrical heating elements placed between the external fins and within the are bounding the outer edges of the external ns, dielectric cemenet lling the space between the heating elements and the ns, and heat-insulating material surrounding each of the runs of the tubing.

7. A liquid heater comprising a continuous length of extruded seamless aluminum tubing arranged in a plurality of runs connected by bends, the runs having external and internal spiral ns homogeneously integral with the tube, the internal ns being arranged directly opposite external ns of the tubing, the bends having internal fins only, electrical heating elements placed between the external ns and within the arc bounding the outer edges of the external fins, dielectric cement filling the space between the heating elements and the fins, and heateinsulating material surrounding each of the runs of the tubing. i

WALTERYE. GILLESPIE. 

